Covalently bonding nail primer

ABSTRACT

The present invention relates generally to the field of primers and adhesion promoters. More specifically, the primer of the present invention is comprised of one or more multi-carbonylated methacrylates. In a preferred embodiment, a non-ketone polar solvent is also employed. The resulting composition eliminates primer related discoloration of artificial nail enhancements, eliminates the potential for corrosion of skin and nails, and eliminates risk of chemical burn injury, while providing stronger adhesion than currently available primers.

FIELD OF THE INVENTION

[0001] The present invention relates generally to the field of primersand adhesion promoters. More specifically, the primer of the presentinvention is comprised of one or more multi-carbonylated methacrylates.In a preferred embodiment, a non-ketone polar solvent is also employed.

[0002] The disclosed primer has particular utility as a primer for nailsand other proteinaceous substrates. For a number of years, nailtechnicians have searched for acceptable substitutes for extremelycorrosive primers that cause yellowing of nail enhancements. These(meth)acrylic acid-based primers (and all other current nail primers)rely on relatively weak hydrogen bonding to achieve interfacial bonding.In contrast, the present invention is a significant advance in the art—anon-corrosive, non-yellowing primer that covalently bonds to the nailplate. In other words, the disclosed primer will not corrode or irritatethe surrounding tissue or nail plate, nor will it discolor theartificial nail enhancement, while simultaneously bonding theenhancement to the keratin substrate far more strongly than currentlyavailable products.

BACKGROUND OF THE INVENTION

[0003] The nail plate (i.e., the natural nail) is primarily composed ofkeratin, a water-insoluble, fibrous protein that is a major structuralcomponent of skin, hair, wool, silk, feathers, scales, nails and hooves.While keratins can obviously differ greatly in their amino acid makeup,hard keratins may all be generally characterized as cross-linkedpolypeptides. Alpha-keratins such as nails and hooves may be furthercharacterized by their relatively higher percentages of the amino acidcysteine. Typically, the alpha-helix coils of the polypeptides arecross-linked with disulphide bonds between adjacent cysteines. Theresulting plate-like cells are cemented to each other with a stickysubstance and held together by rivet-like structures called desmosomes.Many cell layers adhere to each other to form the nail plate—a structurethat resembles a brick and mortar wall.

[0004] Primers are adhesion promoters that improve adhesion byincreasing interfacial compatibility between surfaces, e.g., the nailplate and an applied coating. For example, a coating of nail polish willresist chipping and peeling if a good base coat is used. Base coats aremore compatible with the nail plate than the nail polish. Base coats actas the “go-between” or “anchor”, to improve adhesion.

[0005] Primers are also frequently used with artificial nailenhancements since acrylic nail products normally have poor adhesion tonail plates. In general, nail plate primers can be thought of asdouble-sided sticky tape, joining the nail plate to the nailenhancement. The nail plate surface is made up of chemical groupspossessing specific structures. Primer molecules must match the chemicaland structural characteristics of the nail plate. More particularly, oneend of the primer is reactive with the methacrylate monomers. With thesetypes of primers, physical abrasion of the nail plate is required toachieve proper levels of adhesion to the keratin substrate. Moreover,these acids are corrosive, and if used improperly they can cause damageto the nail plate and surrounding tissue. These acids can also causediscoloration of the nail enhancement and are a leading cause of nailproduct discoloration. This invention eliminates a large percentage ofdiscoloration problems for professional nail technicians. But even moreimportantly, in response to a number of chemical burn injuries,primarily to children, the Consumer Product Safety Commission recentlyissued a regulation requiring child-resistant packaging for allhousehold products containing more than 5% methacrylic acid. However,child-resistant caps increase the risk of spills in the salon as NailProfessionals struggle to remove the cap. This invention solves both theburn injury and child-resistant cap issues because it utilizes anon-corrosive solvent, while still providing the desired adhesionproperties.

[0006] Commercially available nail primers rely solely on hydrogenbonding. Hydrogen bonding on organic substrates such as keratintypically depends on the interaction between an oxygen or nitrogen atomthat is covalently bonded to the upper surface of the nail plate and ahydrogen atom, covalently bonded to methacrylic acid, which iscovalently linked to the polymer. A special type of interaction called ahydrogen bond exists between the interfaces of these dissimilarsurfaces. Hydrogen bonds are types of attractive, intermolecular bondsthat are characteristic of atoms with high electonegativity, i.e.fluorine, oxygen, sulfur, and nitrogen. They are many times weaker thanthe weakest covalent bond, which is found between a carbon and acidichydrogens such as C—H as found in chloroform and acetylene. Thisweakness accounts for the attraction between the acidic hydrogen and anearby organic, acidic hydroxyl group of acrylic or methacrylic acidprimer, as well as the inherent relative weakness of hydrogen bonds. Theoverall strength of the hydrogen bond is determined by the strength ofthis relatively weak carbon/hydrogen bond. It is a controlling factor inhydrogen bond strength. Therefore, when acidic primers are used, theweakest adhesive link will exist between an oxygen molecule on thekeratin surface and the acidic hydrogen of (meth)acrylic acid. Sincecovalent bonds are many times stronger than hydrogen bonding,improvements in adhesive bond strength can be achieved by eliminatingthe hydrogen bond and replacing it with a stronger, more permanent,organic covalent bond.

[0007] It is clear from the foregoing that there are three fundamentalproblems with currently available methacrylic primers and acrylic acidadhesion promoters. First is the corrosive nature of their primarycomponent, methacrylic acid. Second, they create temporary hydrogenbonds that are inherently weaker than covalent bonds, leading to aweaker interfacial adhesive bond between the natural nail plate and theprimer molecule, with a stronger adhesive bond between the primermolecule and the polymer chain of the nail enhancement. Third,acid-based primers are a primary cause of nail enhancementdiscoloration. Fourth, acid-based primers can result in chemical burninjuries.

SUMMARY OF THE INVENTION

[0008] The present invention solves the discoloration and corrosivenessproblems associated with currently available primers by providing thefirst truly non-corrosive, non-yellowing covalently bonding primer. Todate, nail primers and adhesion promoters have been corrosive due totheir use of methacrylic or acrylic acid as the primary component. Thepresent invention does not rely on these problematic components.Previous nail primers relied on relatively weak hydrogen bonding betweennail and primer. The present invention employs components that arecapable of creating continuous covalent bonds from the nail plate to theartificial nail enhancement, providing much improved adhesion.Additionally, previous nail primers were a prevalent cause of yellowingduring “fills” when the primer came into direct contact with existingnail enhancement product on the natural nail. When using traditionalprimers, Nail Professionals must take great care to avoid the acid-basedprimer coming into contact with the artificial nail. Every two weekswhen the artificial nail is “filled in” in the areas of new growth, darkyellow bands appear across the width of the nail enhancement when the(meth)acrylic acid primer comes into contact with the existingenhancement polymer.

[0009] These and other advantages are accomplished by the presentinvention, which relates to a primer comprised of one or moremulti-carbonylated methacrylates. In a preferred embodiment,acetoacetoxy ethyl methacrylate (“AAEMA”) is reacted withpolyoxypropylenetriamine to produce an imine, or Schiff base, in anequilibrium reaction. In alternative embodiments,triethyleneglycoldiamine or other primary amines can be used instead oftriethyleneglycoldiamine to achieve similar results. Simultaneous withthis imine reaction, an amine group of the polyoxypropylenetriamine mayalso react with a carbonyl ester group of AAEMA to form an amide.Finally, the Schiff base undergoes a further electron rearrangementreaction in which an electron shifts to the beta carbon of theacetoacetoxy group (as shown below).

[0010] The resulting composition does not exhibit undesirable corrosiveproperties and is not based on (meth)acrylic acid and, in fact, containsno acidic functionality. Moreover, the disclosed primer providesstronger adhesion than any commercially available nail primer because itallows certain amino acid functional groups on the surface of the nailplate to covalently bond with carbonyl groups in the primer, creatingmuch stronger linkages than can be achieved with hydrogen bonding oftraditional primers.

[0011] Other objects, features, and characteristics of the presentinvention, as well as the methods of operation and functions of therelated elements of the structure, and the combination of parts andeconomies of manufacture, will become more apparent upon considerationof the following detailed description, which forms part of thisspecification.

DETAILED DESCRIPTION OF THE INVENTION

[0012] As required, a detailed illustrative embodiment of the presentinvention is disclosed herein. However, techniques, systems, andoperating structures in accordance with the present invention may beembodied in a wide variety of forms and modes, some of which may bequite different from those in the disclosed embodiment. Consequently,the specific structural and functional details disclosed herein aremerely representative, yet in that regard, they are deemed to afford thebest embodiment for purposes of disclosure and to provide a basis forthe claims herein, which define the scope of the present invention. Thefollowing presents a detailed description of a preferred embodiment (aswell as some alternative embodiments) of the present invention.

[0013] The present invention is a dramatically improved primer that isparticularly appropriate for use with nails. Herein, “nail” refers tonot only human nails, but also nails and hooves of animals, and anyother hard surface proteinaceous materials. The nail primer of thepresent invention is principally comprised of multi-carbonylatedmethacrylates dissolved in a suitable solvent or other delivery system.In a preferred embodiment of the present invention, the aforementionedcomponents may be diluted in polar non-ketone solvents, however,non-polar solvents will work as well.

[0014] Various formulas have been tested by the applicant. One preferredembodiment comprises a polyether amine having a hydrophilic backbone, anacetoacetoxy methacrylate, and a polar non-ketone solvent. Of course,other components can be substituted as described below. One preferredpolyether amine is triethyleneglycoldiamine. Again, other similarcomponents (such as polyoxypropylenetriamine) can be utilized to achievethe results of this invention.

[0015] The preferred amines contain two or three primary aminefunctional groups, respectively. The primary amine functional groups arelocated on secondary carbon atoms at the ends of aliphatic polyetherchains. Other primary amines, including monofunctional, difunctional andtrifunctional amines, may be used in the present invention to achievethe desired results. Such primary amines include all polyetheramines,including but not limited to polyethyleneglycolamine,polyoxypropyleneamine, polyethyleneglycol-polyoxypropyleneamine,polyoxypropylenediamine, polyethyleneglycol-polyoxypropylenediamine,polyethyleneglycoltriamine, polyethyleneglycol-polyoxypropylenetriamine.Some examples of the above-mentioned components include, but are notlimited to melamine, N,N-dimethylformamide, 1,5-diaminopentane anddibutylamine.

[0016] One particularly preferred multi-carbonylated methacrylate isacetoacetoxy ethyl methacrylate (referred to herein as “AAEMA”).

[0017] The preferred solvent of the present invention is a non-ketonesolvent. This ensures that the solvent will not react with the carbonylgroup in the methacrylate, nor compete with the AAEMA carbonyl reaction.In nail applications, this helps prevent yellowing of the nailenhancement. However, in alternative embodiments of the invention whereperhaps a slight coloration to the solvent blend would not beobjectionable, a ketone solvent can be utilized if appropriateconditions are used during the bulk chemical reaction.

[0018] The solvent utilized in the present invention is also preferablya polar solvent to minimize the amount of discoloration which isobserved when a non-polar solvent is utilized. However, in alternativeembodiments of the present invention, a non-polar solvent can beutilized without compromising the integrity of the primer, which retainsits adhesive and non-corrosive properties. Particularly preferred polarnon-ketone solvents include ethanol and isopropanol. Other usefulsolvents include, but are not limited to, ethers, esters, glycol ethers,chlorinated solvents, siloxanes, tetrahydrofuran, methanol and otherhigher molecular weight alcohols, and suitable combinations thereof.

[0019] The weight percentages of the epoxy amine component in the testedformulas ranged from 0.75 to 2.5 percent, while the molar ratios ofAAEMA to amine ranged from 1 to 5. Upon mixing, the carbonyl group ofthe acetoacetoxy group of AAEMA reacts with the primary amine group toform an imine, or Schiff base. In a preferred embodiment, the primaryamine is triethyleneglycoldiamine. This reaction proceeds as follows:

[0020] wherein R represents the remainder of the amine. Other aminegroups may also react with AAEMA. This reaction is followed by electronre-arrangement favoring the beta carbon of the acetoacetoxy group:

[0021] It should also be appreciated that the amine groups can alsoreact with AAEMA ester groups to form an amide:

[0022] Analytical testing using a Liquid Chromatography MassSpectrometer (LC-MS) demonstrates that the imine formation reactiontakes place more readily than the amide formation reaction. Furtheranalytical testing using a Gas Chromatograph Mass Spectrometer (GC-MS)indicates that less than 10 percent of the AAEMA reacted in the amideformation reaction. Additional testing confirms that increasing themolar ratio of AAEMA to amine increases the number of amine functionalgroups that react with AAEMA.

[0023] While the preferred embodiment of the present invention has beenillustrated with the reaction of an AAEMA and a polyether amine (such aspolyoxypropylenetriamine), other multi-carbonyl methacrylate chemicals,and other amines may also be used. By using chemicals with slightlydifferent properties, the resulting primer can effectively adhere to awide variety of surfaces, such as glass, metal, sheetrock, etc., to actas a primer for other applications.

[0024] Comparative testing on the adhesion promoting activity of theimproved primer of the present invention was performed both in alaboratory (with an instrument that tests adhesion) and in the field byprofessional nail technicians. Laboratory testing showed that the primerfunctioned better than its ingredients (amine, AAEMA, and ethanol)individually. More importantly, the nail primer of this invention workedbetter than all other commercially available nail primers tested.

[0025] The following procedure was used in the laboratory testing.First, a clean keratin substrate (hoof) was coated with the testedprimer. A system utilizing ethyl methacrylate monomer liquid and amethacrylate copolymer powder was applied to the top of the primedhoofs. After the monomer and copolymer completely polymerized, adhesiontesting apparatus utilizing a computer controlled assembly, including asharp blade held at a precise angle to the surface of the hoof, was usedto peel or delaminate the methacrylate polymer from the coated keratinsubstrate at a predetermined speed. The force needed to delaminate thepolymer was detected and recorded by the computerized control system.The greater the force needed to peel or delaminate the polymer from thekeratin substrate, the stronger the adhesive bond was to the keratinsubstrate. Table 1 illustrates the results of the laboratory tests:TABLE 1 Adhesion Standard Strength Deviation N N Main IngredientsCompany Advanced 300 65 Methacrylic acid, Pinnacle Formula IsobutylMethacry- Primer late X- 340 60 Methacrylic acid, Star Nail StrengthIsobutyl Methacry- Primer late Original 400 65 Methacrylic acid,International Non- Isobutyl Methacry- Nail Lifting late Manufacturers NoLift 490 105 100% Methacrylic No Lift Nails Primer acid Bondex 500 80Methacryloyloxy- O.P.I ethyl maleate, ethyl acetate Coval- 570 140Polyoxypropylene- Creative Nail ently triamine, AAEMA, Design BondingEthanol Primer

[0026] The improved nail primer of the present invention shows averageadhesion strength of 570 N. The strongest commercially available primerhad adhesion strength of only 500 N.

[0027] The significant increase in strength achieved by the disclosedprimer can be largely attributed to its ability to covalently bond tothe nail plate. As was previously discussed, presently availableprimers, including those identified in Table 1 (other than the presentinvention) are bonded to the nail plate via hydrogen bonding. Incontrast, applicant's primer takes advantage of the greatly increasedbond strengths attained through covalent bonding.

[0028] Obviously, with individual differences in both keratins and nailsurfaces, a number of covalent reaction mechanisms are possible. It isanticipated, however, that two reactions will dominate. Because of thesurprisingly high level of adhesion, we believe our data shows that thedominant reaction involves a direct, continuous series of covalent bondsbetween the keratin and the enhancement polymer. In the first, estergroups in the primer react with amines in keratin:

[0029] where R is the rest of the primer. In the alternative reaction,amines in the primer react with carboxylic groups in keratin:

[0030] where R′ is the rest of the primer.

[0031] In any given case, one reaction might dominate over the other, orboth reactions may proceed simultaneously. Those of skill in the artwill appreciate that it is not the precise reaction mechanism that isimportant, but rather the fact that covalent bonding, via one or moremechanisms, is occurring. This is the advance that arguably will makeall previous nail primers obsolete.

[0032] Confirmatory data was also collected in field tests. In a twomonth study, 18 nail technicians performed tests on a total of 429clients. The tests showed that the client's nail enhancements were lesslikely to lift when using the primer of the present invention. Moreover,while discoloration of nail enhancements is inevitable when using aprimer that contains methacrylic acid, use of the primer of the presentinvention eliminated such discoloration. To date, the improved primer ofthe present invention has been field tested on 4,582 people yieldingequally successful results.

[0033] While the present invention has been described with reference toone or more preferred embodiments, which embodiments have been set forthin considerable detail for the purposes of making a complete disclosureof the invention, such embodiments are merely exemplary and are notintended to be limiting or represent an exhaustive enumeration of allaspects of the invention. The scope of the invention, therefore, shallbe defined solely by the following claims. Further, it will be apparentto those of skill in the art that numerous changes may be made in suchdetails without departing from the spirit and the principles of theinvention.

We claim:
 1. A primer comprising: an amine; a multi-carbonylatedmethacrylate; and a solvent.
 2. A primer according to claim 1, whereinsaid solvent comprises a polar non-ketone solvent.
 3. A primer accordingto claim 1, wherein said solvent comprises a non-polar non-ketonesolvent.
 4. A primer according to claim 1, wherein said amine is apolyethyleneglycolamine, polyoxypropyleneamine,polyethyleneglycol-polyoxypropyleneamine, polyoxypropylenediamine,polyethyleneglycol-polyoxypropylenediamine, polyethyleneglycoltriamine,or polyethyleneglycol-polyoxypropylenetriamine.
 5. A primer according toclaim 1, wherein the amine concentration ranges between 0.5 and 20percent inclusively.
 6. A primer according to claim 1, wherein saidmulti-carbonylated methacrylate is acetoacetoxy ethyl methacrylate. 7.An adhesive primer comprising: an amine; an acetoacetoxy ethylmethacrylate; and a solvent.
 8. A primer according to claim 7, whereinsaid solvent comprises a polar non-ketone solvent.
 9. A primer accordingto claim 7, wherein said solvent comprises a non-polar non-ketonesolvent.
 10. A primer according to claim 7, wherein said amine is apolyethyleneglycolamine, polyoxypropyleneamine,polyethyleneglycol-polyoxypropyleneamine, polyoxypropylenediamine,polyethyleneglycol-polyoxypropylenediamine, polyethyleneglycoltriamine,or polyethyleneglycol-polyoxypropylenetriamine.
 11. A primer accordingto claim 7, wherein said amine concentration ranges between 0.5 and 20percent inclusively.
 12. An improved nail primer comprising: an amine; amulti-carbonylated methacrylate; and a solvent.
 13. A primer accordingto claim 12, wherein said solvent comprises a polar non-ketone solvent.14. A primer according to claim 12, wherein said solvent comprises anon-polar non-ketone solvent.
 15. A primer in accordance with claim 12,wherein said amine has a hydrophilic backbone.
 16. A primer inaccordance with claim 12, wherein said amine is apolyethyleneglycolamine, polyoxypropyleneamine,polyethyleneglycol-polyoxypropyleneamine, polyoxypropylenediamine,polyethyleneglycol-polyoxypropylenediamine, polyethyleneglycoltriamine,or polyethyleneglycol-polyoxypropylenetriamine.
 17. A primer accordingto claim 12, wherein said amine concentration ranges between 0.5 and 20percent inclusively.
 18. A primer according to claim 12, wherein saidmulti-carbonylated methacrylate is acetoacetoxy ethyl methacrylate. 19.An essentially non-yellowing nail primer comprising: an amine; amulti-carbonylated methacrylate; and a solvent.
 20. A primer accordingto claim 19, wherein said solvent comprises a polar non-ketone solvent.21. A primer according to claim 19, wherein said solvent comprises anon-polar non-ketone solvent.
 22. A primer in accordance with claim 19,wherein said amine has a hydrophilic backbone.
 23. A primer inaccordance with claim 19, wherein said amine is apolyethyleneglycolamine, polyoxypropyleneamine,polyethyleneglycol-polyoxypropyleneamine, polyoxypropylenediamine,polyethyleneglycol-polyoxypropylenediamine, polyethyleneglycoltriamine,or polyethyleneglycol-polyoxypropylenetriamine.
 24. A primer accordingto claim 19, wherein said amine concentration ranges between 0.5 and 20percent inclusively.
 25. A primer according to claim 19, wherein saidmulti-carbonylated methacrylate is acetoacetoxy ethyl methacrylate.